Understanding the Effects of COVID-19 Vaccines on Reducing Secondary Transmission

• Activity Number: 150 - COVID-19 Vaccine Statistics: A Reflection on a Year at Warp Speed
• Type: Invited
• Date/Time: Tuesday, August 10, 2021 : 10:00 AM to 11:50 AM
• Sponsor: Biometrics Section
• Author(s): Holly Janes*
• Companies: Fred Hutchinson Cancer Research Center
• Keywords: COVID-19 ; vaccine efficacy; clinical trial; transmission; viral load

Abstract

As of Fall 2020, several candidate COVID-19 vaccines had entered Phase 3 trials to determine their safety and efficacy among adults at appreciable risk of SARS-CoV-2 infection and COVID-19 disease. The primary objective of each of these trials was to evaluate vaccine efficacy against COVID-19 disease, with SARS-CoV-2 infection and severe COVID-19 disease as key secondary endpoints. However, it will also be important to determine whether and to what extent these and future vaccines can reduce onward transmission of infection, e.g. through reduced shedding of virus. Understanding this has implications for policy, e.g. impacting whether vaccines are rolled out in populations such as young people who have low burden of disease but transmit infection to more vulnerable populations. In this talk, we will outline trial design approaches to understanding vaccine effects on secondary transmission. A focus will be on understanding the value of SARS-CoV-2 viral load as a surrogate for transmissibility, and strategies for capturing vaccine effects on this endpoint.